This invention relates to a refrigerant compressor primarily for use in an air conditioning system for automotive vehicles, and more particularly to a vane compressor which employs roller bearings to support the drive shaft and has improved lubrication of various sliding portions of the compressor.
Vane compressors are widely employed as refrigerant compressors in air conditioning systems for automotive vehicles, in general, by virtue of their simple construction and adaptability to operation at high rotational speeds. A typical conventional vane compressor of this kind comprises a pump housing formed of a cam ring and front and rear side blocks secured to opposite ends of the cam ring, and accommodating therein a rotor and vanes, a front head to which the front side block is secured, a drive shaft extending through the front and rear side blocks and the front head and journalled by two radial plane bearings formed, respectively, on the front and rear side blocks, and a drive shaft-seal means arranged in a sealing chamber formed in the front head and fitted on the drive shaft to seal same against the front head.
In this conventional vane compressor, the front and rear side blocks are each formed with a radially extending lubricating oil feeding bore and an axially extending oil passage. The lubricating oil feeding bores each have one end opening in the discharge pressure chamber and the other end opening in the surface of the associated radial bearing disposed in sliding contact with the drive shaft. One of the oil passages communicates the sealing chamber with a back pressure chamber which communicates with the bottom of each of the vanes, while the other oil passage communicates an oil chamber disposed to enclose the rear end of the drive shaft with the back pressure chamber. During operation of the compressor, lubricating oil in the discharge pressure chamber is guided through each of the lubricating oil feeding bores and then the clearances between the drive shaft and the radial bearings to be fed into the sealing chamber on one hand, and into the oil chamber on the other hand, to lubricate the sliding surfaces of the above parts. The lubricating oil in the above clearances is also guided to the back pressure chamber to impart a predetermined back pressure to the vanes.
According to the above lubricating feeding system, the lubricating oil under high pressure, stored in the discharge pressure chamber is reduced in pressure by the flow resistance acting upon the lubricating oil as it travels through the clearances between the drive shaft and the plane bearings, so as to impart a required level of pressure to the sealing chamber and the back pressure chamber. In order to achieve such required level of pressure with accuracy, it requires close tolerances in machining the surfaces of the drive shaft and the plane bearings in sliding contact with each other, as well as in assembling these parts. Further, the plane bearings are apt to undergo insufficient lubrication of their sliding surfaces, often resulting in seizure of the bearings and the drive shaft. In addition, extraneous matters can be intruded into the clearances between the bearings and the drive shaft, which also can cause seizure of these parts. Still further, plane bearings in general are inferior to roller bearings in respect of energy consumption. Moreover, the sealing chamber and the oil chamber are supplied with lubricating oil having a high pressure at substantially the same level with the back pressure acting upon the vanes, and having a high temperature, which is heated due to the compressed refrigerant, causing insufficient lubrication and cooling of the bearings and the drive shaft-seal means, as well as leakage of lubricating oil and refrigerant through the sealing chamber.